A system and method to substantially prevent Denial of Service (DoS) attacks due to Random Access Channel (RACH) overload in cellular wireless networks. Once a mobile handset is identified to cause or contribute significantly to a RACH overload of the cell, the system sends a special System Information Block (SIB) message targeted to that mobile handset and instructing it to redirect its RACH signaling to a separate RACH/PRACH (Physical Random Access Channel) resource or to a small part of the current RACH/PRACH resource. This allows most or all of the regular RACH/PRACH resource from being overloaded by a single user or a group of users. The use of a separate RACH/PRACH resource such as frequency, preamble sequence, and/or radio subframe access slot to “absorb” high volume RACH signaling traffic from a small number of malicious/defective mobile handsets substantially prevents the signaling DoS attacks in the wireless network and makes it more robust to such attacks.